Does Milk Make You Smarter? What the Research Shows for IQ

Drinking milk does not make you smarter in any way that a good study has shown. In the best-known randomized trial, Kenyan schoolchildren given a daily cup of milk for nearly two years did not gain on a nonverbal reasoning test the way children given meat did, and a 2025 genetic study of 43,836 older adults found no meaningful effect of dairy intake on general cognition.

Milk does matter in one indirect way. In the UK it is the main dietary source of iodine, and low iodine in pregnancy is linked to lower verbal IQ in children. This page covers why milk got its reputation, what the school-feeding trials and studies of older adults found, where iodine fits in, and the claims about A2 milk and lactose tolerance. It describes research and is not medical or dietary advice.

Milk is nutrient-dense. A glass supplies high-quality protein, calcium, vitamin B12, riboflavin and, in countries where cattle feed is supplemented, a good deal of iodine. Children who are undernourished grow better when they get more animal-source food, and school milk schemes have long been justified on the grounds of child growth and health.

That history makes milk sound like it should help the brain. But a food that corrects a deficiency is different from a food that raises intelligence in people who are already well fed. Most of the research on milk and cognition falls into one of those two situations, and it is important to keep them apart. For the general question of what diet can and cannot do for IQ, see our overview of whether diet or nutrition affects IQ.

The most direct test of milk and children's thinking is the Child Nutrition Project in Embu District, Kenya, a randomized trial run by researchers from UCLA and the University of Nairobi in the late 1990s. Twelve rural primary schools were randomly assigned to four groups. Children in their first year of school received a mid-morning portion of githeri, a local maize-and-bean stew, with meat added, with a cup of milk, or with extra oil to equalize energy. A fourth group received no snack.

• Reasoning: In the first cohort of 555 children, followed for 21 months, the meat group showed the steepest gains on Raven's Progressive Matrices, a nonverbal reasoning test often used as a measure of fluid intelligence. Whaley and colleagues reported that the meat group significantly outperformed all the other groups, including the milk group. There were no group differences in verbal comprehension.

• Arithmetic: A later summary by Neumann and colleagues reported that the meat group and the plain-githeri group improved more on arithmetic tests than both the milk group and the controls.

• School grades: In a second cohort analysed by Hulett and colleagues, children who received githeri plus 250 ml of whole milk did improve more than controls on end-of-term exams in English, Kiswahili, geography and science, though less than the meat group.

• Growth: Milk raised the rate of height gain only among younger and already stunted children.

So milk helped undernourished children in some ways, especially their school marks, but it did not move the closest thing to an intelligence measure in the trial. The study has real limits. Only three schools received each diet, so the effective sample for comparing groups is much smaller than the number of children, and the authors did not report results on an IQ scale. These were children in a rural area where micronutrient deficiencies were widespread, so the results say little about well-fed children in wealthy countries.

Most of the adult research comes from cohort studies of older people, and it does not show a reliable effect.

In the Maine-Syracuse Longitudinal Study, Crichton and colleagues found that 972 adults who ate dairy at least once a day scored higher on several cognitive tests than those who rarely did. The data were cross-sectional (one point in time), so they cannot show which came first, and frequent dairy eaters may differ in other ways.

A 2018 systematic review by Lee and colleagues found only one small trial (38 participants) and seven cohort studies. Pooling three cohorts, high milk intake was not linked to cognitive decline (risk ratio 1.21, with a confidence interval from 0.81 to 1.82, which includes no effect), and the authors rated the evidence as insufficient for any conclusion.

A 2026 meta-analysis in older adults by Giraldo-Castrillon and colleagues found the same null result for observational studies (odds ratio 0.95). Its pooled randomized trials looked more positive, with a standardized difference of 0.45 on global cognition. That figure needs care. It came from five small trials with 369 people in total, most testing specific fermented or fortified dairy products, and the outcomes were cognitive screening tests, not IQ. If it were an IQ effect, it would equal about 7 points (0.45 × 15), which would be far larger than any established nutritional effect in well-fed adults.

The strongest design so far is a Mendelian randomization study, which uses genes that people inherit at random to stand in for a lifetime of diet. Ortega and colleagues used the lactase persistence variant, the gene that lets adults digest milk sugar and so predicts how much dairy they consume, in 43,836 people over 55 in Switzerland, the Netherlands and Canada. They found no effect on a standard screening test of general cognition in the two European cohorts, and the small differences seen in the Canadian cohort did not appear elsewhere. The authors concluded that interventions targeting dairy are unlikely to have a relevant effect on cognitive function.

The most important link between milk and IQ runs through iodine, which the thyroid needs to make hormones that guide fetal brain development. In the UK, where salt is not routinely iodized, milk is the principal source of iodine in the diet.

Bath and colleagues measured iodine in stored urine samples from 1,040 pregnant women in the Avon Longitudinal Study of Parents and Children (ALSPAC) and followed their children. After adjusting for 21 background factors, children of women with low iodine early in pregnancy were more likely to score in the bottom quarter for verbal IQ at age 8 (odds ratio 1.58) and for reading at age 9. The lower the mother's iodine, the worse the children's scores tended to be. This is observational evidence about mild deficiency, and it concerns the mother's intake in pregnancy, not the child's milk drinking.

A 2026 review by Bath notes that women of childbearing age in the UK are now classed as mildly iodine deficient and that switching from cow's milk to unfortified plant-based drinks may add to the risk. Iodine deficiency and its effects on IQ are covered in depth on our page about iodine and IQ. Anyone pregnant or planning a pregnancy who is unsure about iodine should ask a doctor, midwife or dietitian.

Two other claims circulate online. The first is that A2 milk, from cows that produce only the A2 form of beta-casein protein, sharpens thinking. The main study behind this gave 80 Chinese preschoolers with milk intolerance each type of milk for five days. Children improved in accuracy on a brief computer task after A2 milk compared with their own baseline. The trial was funded by The a2 Milk Company, and one author co-directed the company that owns the cognitive test. It says nothing about IQ.

The second claim links national rates of lactose tolerance or milk drinking to national IQ estimates. Country-level correlations like these mix together wealth, schooling, health care and many other differences, and the Mendelian randomization study above, which tested the lactase gene within populations, found no meaningful effect.

No study has shown that drinking milk raises IQ. In a Kenyan school trial, milk improved some school grades but not reasoning test scores, and a genetic study of 43,836 adults found no meaningful effect of dairy on general cognition.

Milk can help undernourished children grow and may help their school performance. In well-fed children there is no good evidence that extra milk raises intelligence.

Breastfeeding is a separate question with its own large literature, covered on our page about breastfeeding and IQ.

In the UK, milk is the main dietary source of iodine, and low iodine in early pregnancy is linked to lower verbal IQ scores in children. People who avoid dairy and are pregnant or planning a pregnancy should talk to a doctor, midwife or dietitian.

The only cognitive data come from a five-day, company-funded study of 80 preschoolers with milk intolerance using a brief computer task. That is not evidence that A2 milk raises intelligence.

Milk is a useful food, especially for children who would otherwise go short of protein and micronutrients, but it does not make you smarter. In the Kenyan trial only the meat snack improved reasoning scores, cohort studies of adults are inconsistent, and a genetic study of more than 40,000 people found no meaningful effect. The one clear link to IQ is indirect: milk supplies much of the iodine that a developing brain needs before birth. If you want an accurate picture of your own reasoning ability, try a professionally developed IQ test.

1. Whaley, S. E., Sigman, M., Neumann, C., Bwibo, N., Guthrie, D., Weiss, R. E., Alber, S., & Murphy, S. P. (2003). The impact of dietary intervention on the cognitive development of Kenyan school children. The Journal of Nutrition, 133(11 Suppl 2), 3965S-3971S. [doi.org/10.1093/jn/133.11.3965S](. doi.org

2. Neumann, C. G., Murphy, S. P., Gewa, C., Grillenberger, M., & Bwibo, N. O. (2007). Meat supplementation improves growth, cognitive, and behavioral outcomes in Kenyan children. The Journal of Nutrition, 137(4), 1119-1123. [doi.org/10.1093/jn/137.4.1119](. doi.org

3. Hulett, J. L., Weiss, R. E., Bwibo, N. O., Galal, O. M., Drorbaugh, N., & Neumann, C. G. (2014). Animal source foods have a positive impact on the primary school test scores of Kenyan schoolchildren in a cluster-randomised, controlled feeding intervention trial. British Journal of Nutrition, 111(5), 875-886. [doi.org/10.1017/S0007114513003310](. doi.org

4. Crichton, G. E., Elias, M. F., Dore, G. A., & Robbins, M. A. (2012). Relation between dairy food intake and cognitive function: The Maine-Syracuse Longitudinal Study. International Dairy Journal, 22(1), 15-23. [doi.org/10.1016/j.idairyj.2011.08.001](. doi.org

5. Lee, J., Fu, Z., Chung, M., Jang, D. J., & Lee, H. J. (2018). Role of milk and dairy intake in cognitive function in older adults: A systematic review and meta-analysis. Nutrition Journal, 17, 82. [doi.org/10.1186/s12937-018-0387-1](. doi.org

6. Giraldo-Castrillon, Y., Mendoza, J. D., Lopez-Cabrera, M., Lopez-Lopez, J. P., & Lopez-Jaramillo, P. (2026). Effect of milk and dairy intake on cognitive function in older adults: A systematic review and meta-analysis. Frontiers in Aging, 7, 1709281. [doi.org/10.3389/fragi.2026.1709281](. doi.org

7. Ortega, N., Mueller, N. J., Dehghan, A., de Crom, T. O. E., von Gunten, A., Preisig, M., ... Chocano-Bedoya, P. O. (2025). Dairy intake and cognitive function in older adults in three cohorts: A Mendelian randomization study. Nutrition Journal, 24, 20. [doi.org/10.1186/s12937-025-01083-y](. doi.org

8. Bath, S. C., Steer, C. D., Golding, J., Emmett, P., & Rayman, M. P. (2013). Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: Results from the Avon Longitudinal Study of Parents and Children (ALSPAC). The Lancet, 382(9889), 331-337. [doi.org/10.1016/S0140-6736(13)60436-5](. doi.org

9. Bath, S. C. (2026). Iodine deficiency in the UK: Should we take it with a pinch of salt? Proceedings of the Nutrition Society. Advance online publication. [doi.org/10.1017/S0029665125102164](. doi.org

10. Sheng, X., Li, Z., Ni, J., & Yelland, G. (2019). Effects of conventional milk versus milk containing only A2 β-casein on digestion in Chinese children: A randomized study. Journal of Pediatric Gastroenterology and Nutrition, 69(3), 375-382. [doi.org/10.1097/MPG.0000000000002437](. doi.org

Hero image: Abbotts Glass Milk Bottles 1920s-1960s, by Bruce C. Cooper, CC BY-SA 4.0. Via Wikimedia Commons.